Electrostatic discharge, as well as the mere presence of a static electric field, can be extremely detrimental to sensitive electronic (solid-state) parts. Modern semiconductors and integrated circuits may be degraded or destroyed by such static buildup. One common tool used to control static discharge and buildup is a conductive grounding tether which is designed to drain away excess electrostatic charge. A general discussion of such devices can be found in U.S. Pat. Nos. 4,677,521, 5,018,044, and 5,184,274.
The wristbands and tethers disclosed in these patents have many parts which add to the cost of the devices. While those devices have features which make them advantageous for particular uses, they are relatively expensive when considered for the most basic task of safe and effective grounding. Less expensive and simpler bands have been designed, such as those shown in U.S. Pat. Nos. 3,857,397 and 4,698,724, but those designs suffer from certain inherent limitations. For example, both of these designs are unitary wristband/tethers, meaning that if the tether portion of the device breaks, the wristband becomes useless, or vice-versa, and also meaning that if the user desires to walk away from his or her workstation he or she must completely take off the wristband, or must allow the tether portion to dangle, in contrast with the designs that allow the tether to be detachably connected to the wristband. Both of these designs are also ill-suited for use in a dual conductor system (such as that shown in the '044 patent). Finally, the means for adjusting the effective size of the wristband must be applied separately to the band, such as the hook-and-loop fastening strips in the '397 patent, or the adhesive layer in the '724 patent This separate application step increases processing cost, but it is critical that the device achieve a proper exact adjustment since it must have good contact with the skin to be sufficiently conductive, and yet not be so tight to constrict circulation or otherwise be uncomfortable.
Alternatives to the hook and loop fastening described in the '397 patent require pressing together overlapping portions of a strap to establish interlocking contact to secure the strap in a looped configuration of desired dimensions. For example, U.S. Pat. Nos. 3,514,815, 3,518,727, and 4,872,242 provide elongated, flexible straps with means on their upper and lower surfaces for connection between surfaces. When formed into a loop, the straps are positioned with teeth on one surface adjacent to valleys on the opposite surface. The teeth and valleys will nest together, under suitable pressure, so that interlocking connection between teeth and valleys occurs. Upon wrapping one of the disclosed flexible straps around, for example, a cable bundle, the teeth and valleys provide interlocking means capable of self-engagement along a length where the strap overlaps itself.
U.S. Pat. Nos. 4,178,751 and 4,941,236 disclose interlocking structures for securing straps, associated with watches, around the wearer's wrist. The '236 patent discloses an interlocking means in the form of a clasp for a watch band. In this case the free end portions of the band include magnetic segments. End portions may be secured together under the influence of the magnetic force. The strap ends have surfaces contacting one another where they overlap with mutually nesting, uniformly spaced interlocking teeth; the magnetic segments provide a holding force resisting separation of the end portions while the nested teeth prevent sliding disengagement between the ends. In the '751 patent, an injection-molded casing for a watch module includes an integrally molded wristband. The casing also includes a metal form partially covered by integrally molding a thermoplastic material over the form and may, by design, leave sections of the underlying metal exposed. Attachment of the wristband to the wearer's wrist involves clasp portions that nest together, held by interlocking projections formed at the edges of the clasp portions.
Known fasteners, including hook and loop strips and interlocking structures, present some difficulties when adjusting the loop size of a strap. The fastening characteristics of hook and loop closures ensure that, whenever the hooked material and the looped fabric are near each other they tend to cling to one another. Premature clinging may occur requiring several attempts to adjust the loop to the desired size. The hook portions pick up undesirable debris like lint, hair, and other fibrous matter that impairs performance. Interlocking straps include molded rib structures that need aligning before interlocking the fastener components, and may be difficult to remove or may otherwise be inflexible.
It would, therefore, be desirable and advantageous to devise a durable low-cost, low-part count wristband (which can be made of a flexible polymer or polymeric material) with secure fastening, easy removal and convenient strap loop size adjustment.